|MadSci Network: Engineering|
This is really a very interesting question. It took me more than an hour to research it, but I learned a few things in the process. The first point I should make is that scientists don't agree on whether nickel in foods really causes a problem in people sensitive to nickel (Veien NK. Ingested food in systemic allergic contact dermatitis. Clinics in Dermatology. 15(4):547-55, 1997). This same point is also noted on the website: http://allergies.about.com/health/allergies/library/weekly/aa011000a.htm Another webpage from a fairly reputable site (Mayo Clinic Foundation) (http://220.127.116.11/mayo/askdiet/htm/new/qd990317.htm) indicated that soda would not be a problem for nickel sensitive people, while "Chocolate and cocoa drinks, tea from dispensers" should be avoided. I could find no evidence that aluminum cans contain any significant amount of nickel. So do you have a nickel allergy *from* drinking soda? ... Probably not. Should you avoid soda because it would aggravate your contact dermatitis nickel allergy? ... Probably not. Should you avoid certain foods if you have a nickel allergy? ... Maybe, but the science on this point is still in its infancy. The foods to be avoided can be found on the Mayo Foundation webpage above.
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